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annotate libtwamr/sqrt_l.c @ 585:3c6bf0d26ee7 default tip

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TW-TS-005 reader: fix maximum line length bug TW-TS-005 section 4.1 states: The maximum allowed length of each line is 80 characters, not including the OS-specific newline encoding. The implementation of this line length limit in the TW-TS-005 hex file reader function in the present suite was wrong, such that lines of the full maximum length could not be read. Fix it. Note that this bug affects comment lines too, not just actual RTP payloads. Neither Annex A nor Annex B features an RTP payload format that goes to the maximum of 40 bytes, but if a comment line goes to the maximum allowed length of 80 characters not including the terminating newline, the bug will be triggered, necessitating the present fix.
author Mychaela Falconia <falcon@freecalypso.org>
date Tue, 25 Feb 2025 07:49:28 +0000
parents 8dfb7cbe6b59
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 /*
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2 ********************************************************************************
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3 *
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4 * GSM AMR-NB speech codec R98 Version 7.6.0 December 12, 2001
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5 * R99 Version 3.3.0
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6 * REL-4 Version 4.1.0
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7 *
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8 ********************************************************************************
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9 *
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10 * File : sqrt_l.c
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11 * Purpose : Computes sqrt(L_x), where L_x is positive.
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12 * : If L_var is negative or zero, the result is 0
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13 * Description :
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14 * The function sqrt(L_x) is approximated by a table and linear
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15 * interpolation. The square root is computed using the
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16 * following steps:
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17 * 1- Normalization of L_x.
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18 * 2- If exponent is even then shift right once.
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19 * 3- exponent = exponent/2
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20 * 4- i = bit25-b31 of L_x; 16<=i<=63 because of normalization.
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21 * 5- a = bit10-b24
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22 * 6- i -=16
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23 * 7- L_y = table[i]<<16 - (table[i] - table[i+1]) * a * 2
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24 * 8- return L_y and exponent so caller can do denormalization
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25 *
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26 ********************************************************************************
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27 */
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28 /*
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29 ********************************************************************************
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30 * MODULE INCLUDE FILE AND VERSION ID
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31 ********************************************************************************
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32 */
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33 #include "namespace.h"
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34 #include "sqrt_l.h"
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35
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36 /*
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37 ********************************************************************************
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38 * INCLUDE FILES
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39 ********************************************************************************
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40 */
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41 #include "typedef.h"
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42 #include "basic_op.h"
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43 #include "no_count.h"
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44
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45 /*
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46 ********************************************************************************
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47 * LOCAL VARIABLES AND TABLES
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48 ********************************************************************************
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49 */
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50 #include "sqrt_l.tab" /* Table for sqrt_l_exp() */
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51
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52 /*
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53 ********************************************************************************
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54 * PUBLIC PROGRAM CODE
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55 ********************************************************************************
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56 */
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57
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58 Word32 sqrt_l_exp (/* o : output value, Q31 */
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59 Word32 L_x, /* i : input value, Q31 */
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60 Word16 *exp /* o : right shift to be applied to result, Q1 */
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61 )
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62 {
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63 /*
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64 y = sqrt(x)
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65
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66 x = f * 2^-e, 0.5 <= f < 1 (normalization)
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67
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68 y = sqrt(f) * 2^(-e/2)
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69
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70 a) e = 2k --> y = sqrt(f) * 2^-k (k = e div 2,
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71 0.707 <= sqrt(f) < 1)
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72 b) e = 2k+1 --> y = sqrt(f/2) * 2^-k (k = e div 2,
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73 0.5 <= sqrt(f/2) < 0.707)
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74 */
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75
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76
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77 Word16 e, i, a, tmp;
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78 Word32 L_y;
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79
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80 test ();
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81 if (L_x <= (Word32) 0)
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82 {
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83 *exp = 0; move16 ();
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84 return (Word32) 0;
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85 }
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86
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87 e = norm_l (L_x) & 0xFFFE; logic16 (); /* get next lower EVEN norm. exp */
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88 L_x = L_shl (L_x, e); /* L_x is normalized to [0.25..1) */
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89 *exp = e; move16 (); /* return 2*exponent (or Q1) */
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90
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91 L_x = L_shr (L_x, 9);
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92 i = extract_h (L_x); /* Extract b25-b31, 16 <= i <= 63 because
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93 of normalization */
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94 L_x = L_shr (L_x, 1);
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95 a = extract_l (L_x); /* Extract b10-b24 */
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96 a = a & (Word16) 0x7fff; logic16 ();
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97
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98 i = sub (i, 16); /* 0 <= i <= 47 */
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99
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100 L_y = L_deposit_h (table[i]); /* table[i] << 16 */
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101 tmp = sub (table[i], table[i + 1]); /* table[i] - table[i+1]) */
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102 L_y = L_msu (L_y, tmp, a); /* L_y -= tmp*a*2 */
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103
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104 /* L_y = L_shr (L_y, *exp); */ /* denormalization done by caller */
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105
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106 return (L_y);
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107 }